Traditional semiconductor manufacturing gas delivery systems consist of components that are welded together with stainless steel tubing. These systems require a large footprint. It is also difficult to change components since they are welded together. Additionally, the weld creates a heat affected area that is prone to corrosion and particle generation.
The new Modular Surface Mount (MSM) technology allows for a much smaller footprint. The components are instead bolted together with a metal seal between components. This creates a much more flexible system for changing components and configurations. The MSM technology also eliminates welding and therefore the heat affected areas. Critical to the success of the MSM technology is an ultra-low leak rate metal seal that is suitable for the cleanliness requirements of the semiconductor industry.
MSM gas delivery systems are used for controlling and modifying gas supplies for the semiconductor industry. These systems generally comprise stainless steel machined blocks that bolt together. There is a plurality of orifices on the top of the blocks. Modular components, such as filters, flow regulators, pressure transducers, pressure switches, valves and the like, are mounted on top of the blocks and the gas path is defined by providing gas from and through the orifices. At every orifice/component juncture, there must be a seal to prevent gas from leaking and contaminates from migrating into the system. For the semiconductor industry ultra-clean, corrosion resistant metal seals are required. These seals must provide very low leakage and minimize distortion or damage to the flange and hardware interfaces with which they are associated. To facilitate handling of small seals in clean room environments, seals are installed in thin metal sheets referred to as retainers. The seals are inserted into holes in the retainers that hold the seals in place during installation. This seal assembly, consisting of a retainer and a plurality of individual seals, is then installed in the interface between modular components. These systems have developed to have standardized interfaces wherein the block size and orifice size and position are uniform throughout the industry. This allows seals to be used universally in most MSM gas delivery systems.
Prior art seals and seal assemblies are shown in FIGS. 1-4. FIGS. 1 and 2 show a typical “C” seal with a helical spring. The seal 10 has a ductile jacket 20 surrounding a helical spring 30. The ductile jacket 20 does not completely enclose the spring 30 leaving a gap 22 that acts to hold the seal in the retainer 50. This configuration allows the seal 10 to be compressed between the modular components with the spring 30 providing force required to plastically deform the load concentrating projections. The complexity of seals of this nature may introduce manufacturing inconsistencies that result in reduced performance.
FIGS. 3 and 4 show a retainer 50 comprising a thin metal sheet with two seal retaining apertures 52 and four fastener holes 60. Relief cuts 54 in the plate allow seals 10 to be installed into the seal-retaining aperture 52. One disadvantage to this design is the propensity for seals to fall out when the retainer is distorted or flexed. Retainers of this design do not provide the positive retention required of such systems.
Examples of other prior art seals for such applications are disclosed in U.S. Pat. No. 6,043,121 to Ma et al. and U.S. Pat. No. 6,409,180 to Spence et al. The metallic rings disclosed therein are formed with a plastically deformable column configured to buckle under an applied load. They generally comprise two flat sealing surfaces with an internal annular groove in the column to allow the seal to be deformed.
It would be desirable to have an effective seal for use in MSM gas delivery systems and other applications where a leak tight, low contamination seal is required. Furthermore, it would be beneficial to have such a seal made of one part to minimize the complexity and thus, propensity for failure. It would further be desired to have such a seal with a design that is simple and adaptable to many other sealing applications.